1. Field of the Invention
The present invention relates to a turbo decoder. More particularly, the present invention relates to a method and apparatus for controlling iterative decoding in a turbo decoder.
2. Description of the Related Art
For wireless communication, Forward Error Correction (FEC) is used to correct bursty errors of a radio channel. A major example of FEC codes is turbo code. It is known that efficiency closest to the theoretical maximum channel capacity can be achieved by configuring a turbo encoder with two component encoders and an interleaver.
A turbo decoder is the counterpart of a turbo encoder, and generally includes two component decoders serially connected to each other. The turbo decoder iterates decoding by feeding back the output of the second component decoder to the input of the first component decoder, thus increasing decoding efficiency. This scheme is called iterative turbo decoding or turbo iteration.
To maximize the effects of iterative turbo decoding, it is preferable to set the maximum number of iterations to a substantially large number. Without limitations on system resources, overall system performance increases with the number of turbo iterations. Accordingly, if there is no limit on resources and no problems such as heat emission from hardware occur, the number of turbo iterations may be set to a large number. If the maximum number of iterations is large enough, Cyclic Redundancy Check (CRC) decoding performance can be maximized.
However, if heat emission needs to be reduced or receiver resources are limited, as is generally the case for software modems, the number of turbo iterations necessary to achieve a required performance is not ensured. Conventionally, the maximum number of turbo iterations is fixed, taking into account a total system computation volume and a memory capacity. This conventional technology has limitations in its effectiveness to improve turbo iteration-based performance.